There are presently available many types of safety glass structures which may be employed as vehicular lights (e.g. automotive windshields), architectural windows (e.g. skylights), or in various other commercial and industrial contexts. Safety glass structures can be classified into two basic categories, namely, laminated safety glass windows and bilayer windows.
Laminated safety glass windows generally include two plies of glass or other rigid transparent or translucent substrate laminated to an interlayer of polyvinyl butyral, polyurethane, or other suitable transparent or translucent plastic film. To be useful as a laminated safety glass window, a laminate must possess the following properties over a wide range of temperature and moisture conditions: (1) high energy absorption to minimize concussive injuries on impact, (2) prevention of rupture of the film by glass fragments, (3) sufficient adhesion between the layers to minimize dispersion of glass fragments, thereby reducing the potential for lacerative injury, and (4) good optical quality. Representative examples of laminated safety glass windows and methods of producing/manufacturing the same are taught in U.S. Pat. Nos. 2,725,320; 3,027,288; 3,074,466; 3,700,542; 3,769,288; 3,881,043; 3,852,136; 4,062,887; and, 4,180,426.
Bilayer windows generally include a rigid transparent or translucent substrate laminated to a layer of protective transparent or translucent plastic material. The protective layer is usually provided on the surface of the substrate facing the interior of the window-protected environment, and is therefore often referred to as the innerlayer or innerliner, as opposed to an interlayer. The rigid substrate may comprise a single transparent or translucent glass (or other rigid material) substrate, or a laminated safety window. Bilayer windows are designed to minimize facial lacerations attributable to sharp edges of broken glass of the inner glass ply and to absorb concussive forces occurring under impact conditions, more so than conventional laminated safety glass windows which are not provided with a protective plastic layer in covering relation to the inner glass ply. The protective plastic coating or innerliner prevents a person disposed interiorly thereof from coming into contact with the glass. Bilayer windows, especially those wherein the rigid substrate comprises a laminated safety window, when employed as an automotive windshield, are sometimes referred to as antilacerative windshields. The terms "bilayer window" and "antilacerative window" as used herein throughout are interchangeable, and both are intended to convey the meaning of a window comprised of a rigid transparent or translucent substrate laminated to a transparent or translucent protective layer constructed of a material, usually a plastic material, possessing antilacerative properties. Representative examples of bilayer or antilacerative windows and methods for manufacturing the same are taught in U.S. Pat. Nos. 3,781,184; 3,808,077; 4,107,366; 4,109,055; 4,153,526; 4,232,080; and 4,362,587, all teachings of which are herein incorporated by reference.
Although there are presently available many different methods for assembling and laminating the various components of a bilayer or antilacerative window, such as those taught in the above-delineated patents, all of these methods can be said to be comprised of the following basic steps: (1) assembling the rigid substrate and the innerliner in conforming, juxtaposed relation to each other, to provide a bilayer assembly; (2) removing any trapped gases or air from the interfacial spaces between the various plies or layers of the bilayer assembly, usually by means of pulling a vacuum around the peripheral edges of the assembly; and, (3) subjecting the assembly to heat and pressure conditions sufficient to firmly bond or laminate the various plies or layers together, usually within an air and/or oil autoclave. A molding or pressing plate, sometimes referred to as a laminating mold or pressing ply, having a surface contour matching or closely conforming to the surface contour of the rigid substrate, is placed against the exposed face of the innerliner during the degassing and laminating steps, to ensure application of uniform pressure against the innerliner, thereby minimizing the occurrence of optical defects.
A problem which has apparently not yet been addressed heretofore is the problem of removing selected portions of the innerliner to accommodate or facilitate the mounting or attachment of appurtenances, accessories, or other objects or structures to the inner surface of the rigid substrate. Prior to the advent of the present invention, applicant knew of only one feasible technique for cutting out a selected portion of the innerliner to expose a selected portion of the adjacent or inner surface of the rigid substrate. An exemplary situation is the problem of affixing a rear view mirror to a bilayer or antilacerative windshield. The presently known technique is to manually cut a patterned hole into the innerliner at the location whereat the rear view mirror is desired to be mounted. The patterned hole is made to conform to the size and shape of an adhesive pad or "button" which is inserted into the patterned hole to secure the rear view mirror to the inner surface of the rigid substrate. The innerliner is usually cut with a razor blade or other manual cutting tool. The actual hole cutting operation, in accordance with the heretofore known technique, is performed subsequent to the completion of the laminating step. This is necessary, because if the hole were cut out before the laminating step, the innerliner material, or in some cases, the adhesive material employed to adhere the innerliner material to the inner surface of the rigid substrate, would flow into the hole, due to the heat and pressure experienced concomitant with the laminating step, thereby frustrating the objective of exposing the inner glass surface. Additionally, if the innerliner material flows into the hole it may also cause optical defects in the innerliner, and/or cause undesirable binding of the innerliner to the molding or pressing plate.
Several disadvantages are inherent with the above-described heretofore known technique. First of all, the positioning or locationing of the hole is subject to variation and inaccuracy attributable to human error. Secondly, the manual hole cutting step represents an additional step in the overall antilacerative windshield production process. Thirdly, the manual hole cutting step is time consuming and labor intensive, thereby entailing production inefficiencies. Fourthly, manual cutting can cause damage to the underlying rigid substrate. Further, the only technique heretofore known by applicant for cutting the innerliner to the desired size and shape encompasses manually cutting a sheet of innerliner material with a razor blade or other type of manual cutting tool. This manual cutting step is time-consuming, labor intensive, and susceptible to human error, all of which are drawbacks to the overall efficiency of the laminated window production process.
It would therefore be advantageous to have a method for manufacturing a laminated window which overcomes the disadvantages and drawbacks of the heretofore known method.